The present invention relates to systems for arresting a patient""s heart and maintaining a patient on cardiopulmonary bypass. Such systems are used when performing surgical procedures, such as coronary artery bypass grafting, on an arrested heart.
In conventional open-heart surgery, the patient""s breast bone is sawed open, the chest is spread apart, and the heart is accessed through the large opening created in the patient""s chest. The patient is placed on cardiopulmonary bypass and the patient""s heart is then arrested using catheters and cannulae which are inserted directly into the large arteries and veins attached to the heart through the large opening in the chest. The arterial cannula typically passes through the wall of the ascending aorta and a cross-clamp is applied to the ascending aorta to isolate the coronary arteries from the remainder of the arterial system. A venous cannula passes through the right atrium for withdrawing blood from the patient.
Recent developments in cardiac surgery have enabled surgeons to perform coronary artery bypass grafting and valve repair and replacement procedures without creating a large opening in the patient""s chest. These developments have significantly reduced trauma to the patient by eliminating the need for sawing open the breast bone and opening the patient""s chest. Such procedures are disclosed in U.S. Pat. Nos. 5,452,733 and 5,571,215 which are hereby incorporated by reference.
In order to perform such surgical procedures, the patient""s heart must be arrested and the patient placed on cardiopulmonary bypass without direct access to the heart. Catheters and cannulae for arresting the patient""s heart and establishing bypass without requiring direct access to the patient""s heart are disclosed in U.S. Pat. Nos. 5,584,803 and 5,558,644 which are hereby incorporated by reference.
The systems described in U.S. Pat. Nos. 5,584,803 and 5,558,644 include an aortic occlusion device which has a balloon to occlude the ascending aorta and a lumen to deliver cardioplegic fluid for arresting the patient""s heart. The aortic occlusion device replaces the conventional external cross-clamp and advantageously reduces the amount of displacement and distortion of the aorta. Minimizing distortion of the aorta may reduce the amount of emboli released and, therefore, may reduce stroke incidents.
A venous cannula withdraws blood from the patient and blood is returned to the patient through an arterial cannula which is placed at a peripheral artery such as the femoral artery. In a preferred embodiment, the aortic occlusion device passes through the arterial cannula thereby minimizing the number of penetrations in the patients vascular system.
The systems described in U.S. Pat. Nos. 5,584,803 and 5,558,644 also include an endovascular coronary sinus catheter for retrograde perfusion of a cardioplegic agent, preferably blood cardioplegia, via the coronary sinus. The coronary sinus catheter preferably passes through the internal jugular vein and has an inflatable balloon for occluding the coronary sinus. An endovascular venting catheter extends through the tricuspid and pulmonary valves for venting the pulmonary artery.
Although the endovascular bypass system has performed admirably and has enabled surgeons to perform less invasive cardiac procedures, the extracorporeal bypass circuit which couples the catheters and cannulae to the cardiopulmonary bypass elements may be optimized.
Thus, a specific object of the present invention is to provide an extracorporeal flow circuit for use with endovascular cardiopulmonary bypass systems.
In accordance with the present invention, methods and devices for maintaining cardiopulmonary bypass support and arresting the patient""s heart are provided.
In a first aspect of the invention, a method of withdrawing blood from a patient and arresting the patient""s heart is provided. An aortic occlusion device has an occluding member, a lumen and first and second branches coupled to the lumen. The first branch is coupled to a source of cardioplegic fluid, preferably blood cardioplegia, and the second branch is coupled to a pump, preferably a non-occlusive pump such as a centrifugal pump. A venous cannula is also coupled to the pump for withdrawing blood from the patient. The aortic occlusion device is then inserted into the patient so that the occluding member is positioned in the ascending aorta. The occluding member is then expanded to occlude the ascending aorta and cardioplegic fluid is delivered through the lumen in the aortic occlusion device to arrest the patient""s heart. An advantage of the present invention is that a single pump is used for withdrawing blood through the venous cannula and the aortic occlusion device. The single pump reduces the complexity of multi-pump systems.
In another aspect of the present invention, another method of withdrawing blood from the patient is provided. A venting catheter is passed through the patient""s tricuspid and pulmonary valves and a venous cannula is positioned in an artery of the patient. The venting catheter and venous cannula are both coupled to a pump, preferably a non-occlusive pump such as a centrifugal pump. An advantage of coupling the venous cannula and venting catheter to the same pump is that the system becomes self-regulating in that blood is withdrawn through the venous cannula when low flows are achieved through the vent catheter.
In yet another aspect of the invention, a method of withdrawing and returning blood to a patient supported by a bypass system is provided. A venous cannula is inserted into the venous system for withdrawing blood from the patient and an arterial cannula is inserted into the arterial system for returning blood to the patient. A venous line is coupled to the venous cannula and blood is withdrawn from the patient through the venous cannula and venous line. The venous cannula directs the blood to at least one pump which then pumps the blood through an arterial line to the arterial cannula. A blood storage element is coupled to the arterial line and is used to change the amount of blood in the perfusion circuit as needed. In a preferred aspect of the method, an outlet of the blood storage element is coupled to the venous line so that the blood storage element is in parallel with the pump. In another preferred aspect of the invention, the first and second lumens are slidably coupled together. The blood storage element advantageously permits the perfusionist to actively adjust the amount of blood in the perfusion circuit by withdrawing or adding blood to the blood storage element using the pump.
These and other aspects of the invention will become apparent from the following description of the preferred embodiments.